An ordinary high-speed high-pressure injection molding process requires fast mold filling of molten aluminum at a high temperature of about 680° C. During the molding, it is likely to cause internal shrinkage cavity and pore defects due to air entrapment, and accordingly, it is likely to cause poor air tightness in a casting when processed and assembled. After being molded by die-casting, a product is subject to significant thermal deformation during cooling, and the deformation of a die-cast blank can reach about 2 mm. During the cleaning, manual sizing is required to guarantee the planarity that is necessary to the subsequent processing, thus resulting in difficulties in processing and positioning and also adversely impacting the quality and accuracy of the product.
At present, products prepared by ordinary die-casting processes are instable in internal quality, and the assembled products with poor air tightness take share of about 10%. The cleaning of the die-casts is highly labor intensive and it is difficult to guarantee the appearance quality. This becomes a bottleneck procedure for die-casting production and restricts the rapid development of the die-casting industry.
Contents of the Present Invention
A technical problem to be solved by the present invention is to overcome the defects of the prior art, and to provide a die-casting process method for die-cast molding of semisolid metal. With regard to this method, by die-casting of the semisolid slurry, the die-cast product is compact interiorly, without any pores formed, the deformation of a die-cast blank is extremely small, complex surface treatment is not required for the die-cast, and the best quality and performance of the product can be guaranteed.
The present invention provides a die-casting process method for die-cast molding of semisolid metal. In the die-casting process method, a semisolid die-casting machine is used as the processing device, and a pulper is used as the device for preparing and delivering semisolid slurry; the device layout of the die-casting process method is as follows: the pulper is arranged on the left side of the semisolid die-casting machine, a sprayer configured to spray mold release agent to a mold is arranged on the right side of the semisolid die-casting machine, and an extractor configured to extract a die-cast out of the mold is arranged on the front side of the semisolid die-casting machine; the right side of the extractor is coordinated with a conveyor belt, an operating bench is arranged at the right end of the conveyor belt, and an oil press configured to stamp to remove a sprue on the die-cast is provided on the operating bench; and
the die-casting process method includes the steps of:
(1) mounting the mold on the semisolid die-casting machine, spraying the mold release agent onto the surface of the mold with the sprayer, and then closing the mold;
(2) melting metal raw material with a heating furnace, and putting the liquid metal raw material into a holding furnace for storage, wherein the metal raw material is a metal raw material of aluminum alloy;
(3) preparing semisolid slurry from the liquid metal raw material in the holding furnace by the pulper;
(4) conveying the semisolid slurry into the mold of the semisolid die-casting machine by the pulper;
(5) die-casting by the semisolid die-casting machine, and then opening the mold, extracting the die-cast out of the mold with the extractor, and exporting the die-cast by placing it on the conveyor belt; and
(6) conveying the die-cast to the operating bench by the conveyor belt, and stamping to remove the sprue on the die-cast by the oil press to obtain the final die-cast product.
Wherein, in the step (5), the semisolid die-casting machine is a 1000T horizontal cold chamber die-casting machine, with a die-casting temperature of 586° C. to 594° C., a die-casting speed of 4.2 m/s, a system pressure of 15.5 MPa, and a boost pressure of 29 MPa.
Wherein, in the step (3), mass percentages of the components in the liquid metal raw material are: 6-7.5% of silicon, 0.3-1.7% of copper, 0.2-2.5% of zinc, 0.4-2.2% of nickel, 0.2-0.7% of magnesium, 0.2-1.3% of iron, with the balance of aluminum.
Wherein, in the step (3), a method for preparing the semisolid slurry by the pulper comprises the steps of: keeping the temperature of the liquid metal raw material in the holding furnace 12° C. to 23° C. higher than its liquidus; placing the molten metal raw material in the holding furnace into a ladle by the pulper, then placing a solid metal modifier into the ladle, and the metal modifier in the ladle being melted after absorbing the heat of the liquid metal raw material, thus to cool the liquid metal raw material and generate a large number of crystal nuclei, to obtain the semisolid slurry; and blowing, at a speed of 13 L/min, argon gas into the metal raw material in the ladle while adding the metal modifier, to accelerate mixing and cooling, wherein the dosage of the metal modifier is 1.5% to 3.8% of the mass of the metal raw material in the ladle.
Wherein, the components of the metal modifier are the same as those of the liquid metal raw material.
Wherein, the metal modifier comprises the following components: silicon, copper, manganese, magnesium, zinc, titanium, lead and aluminum, at a mass ratio of (6.55 to 6.90):(0.22 to 0.85):(0.003 to 0.008):(0.15 to 0.75):(0.03 to 0.075):(0.06 to 0.1):(0.03 to 0.05):(91.7 to 92.8).
Wherein, the metal modifier comprises the following components: silicon, copper, manganese, magnesium, zinc, titanium, lead and aluminum, at a mass ratio of 6.70:0.57:0.007:0.38:0.047:0.08:0.04:92.5.
According to the above technical solution, the following beneficial technical effects can be found.
(1) With regard to the die-casting process method for die-cast molding of semisolid metal of the present invention, by die-casting of the semisolid slurry, the die-cast product is compact interiorly, without any pores formed, and the best interior structure and mechanical properties of the die-cast product are guaranteed, and the quality of the product is guaranteed.
(2) With regard to the die-casting process method for die-cast molding of semisolid metal of the present invention, by die-casting of the semisolid slurry, compared with the traditional high-speed high-pressure injection molding process, the die-cast, when extracted out of the mold, is lower in temperature, and the die-cast blank, when extracted out of the mold, has a certain mechanical strength. In contrast, a die-cast, prepared by the traditional liquid die-casting processes, when extracted out of the mold, has a higher temperature and is likely to deform when extracted out of the mold. The deformation of the die-cast blank of the present invention is extremely small, and complex surface treatment is not required for the die-cast, so that the best shape and surface smoothness of the product can be guaranteed.
(3) With regard to the die-casting process method for die-cast molding of semisolid metal of the present invention, by a semisolid die-casting process, the die-cast product has many spherical crystals and the die-casting has better mechanical properties.